The present invention relates to shopping carts and the like. In particular, the invention relates to shopping carts of the type having a molded plastic basket and a chassis formed of metal and/or plastic components.
Shopping carts having molded plastic baskets, previously developed by the present inventor, have achieved widespread use and have proved superior to shopping carts with conventional metal wire work baskets. For example, the former are much lighter and have a greater ability to absorb impacts without permanent deformation, and to resist corrosion. Also, they are more easily assembled and taken apart to allow repair or replacement of components since far fewer welded connections are necessary.
A plastic cart design exhibiting the above-described advantages is described in the present inventor's U.S. Pat. No. 3,999,774. In that design, a metal wire reinforcing ring extends around the entire basket opening within a channel provided in an upper peripheral edge of the molded plastic basket side and front panels. A back segment of the wire ring engages the legs of a generally U-shaped cart handle tube provided at the rear of the basket. The cart handle tube legs extend generally vertically along a rear panel of the basket, and are attached at their upper ends by a cross-arm portion providing a cart handle. The lower ends of the cart tubes are attached to a tubular metal base structure carrying front and rear pairs of wheel assemblies.
The inventor's U.S. Pat. No. 4,865,338 discloses an improved reinforcing ring and channel arrangement for the basket of such a plastic cart, or a plastic crate. Therein, specially designed channel protrusions retain the reinforcing ring within a channel without the requirement of channel engaging protrusions on the reinforcing ring.
In carts made in accordance with the above-described patents, the reinforcing ring extends continuously along the entire lengths of the basket side and front panels. Such an arrangement is desirable to lend strength and rigidity to the cart. However, for smaller carts and light-duty applications, a lesser degree of strength and rigidity will suffice, so that such a design may lead to unnecessary material usage for the reinforcing wire. U.S. Pat. No. 4,865,338 recognizes generally that a reinforcing wire may extend about less than the entire periphery of a basket or crate. However, no disclosure is made of how this could be effectively accomplished in connection with a shopping cart, wherein the reinforcing ring braces the basket against the cart handle tube, and is subjected to forces created by downward loads applied to the basket tending to displace the basket relative to the reinforcing ring.
The advantages of a plastic basket construction are taken one step further with the cart designs disclosed in the inventor's U.S. Pat. Nos. 4,746,134 and 4,922,639. In these designs, in place of an all metal frame or chassis, is provided a metal-reinforced plastic chassis. The chassis includes a molded plastic basket support member having a generally horizontally extending base, and an upstanding pedestal structure rising from a rearward portion of the base and providing an elevated basket mounting portion. Cart handle tube legs extend along a rear panel of the basket and terminate at the basket mounting portion. Specially designed wheel mounting brackets are attached to corresponding mounting portions of the plastic base. Conventional caster housings cannot be utilized with these designs and the interchangability of parts among carts is thereby reduced. Furthermore, the mounting brackets required by these designs are more costly to manufacture, chrome plate, and assemble than conventional caster housings.